1. Field of the Invention
The present invention relates in general to a disc cartridge which is widely applied to the data processing field, and more particularly to a shutter which is slidably mounted on the disc cartridge to open and close a recording/reading opening formed in the disc cartridge. More specifically, the present invention is concerned with the shutter, method of producing the shutter and a device for producing the shutter.
2. Description of the Prior Art
In order to clarify the task of the present invention, some conventional shutters for disc cartridges will be briefly described with reference to FIGS. 12 to 14 of the accompanying drawings.
In FIG. 12, there is shown a disc cartridge 201. The disc cartridge 201 comprises generally a disc 202 which is a recording medium, a shell 203 which rotatably receives therein the disc 202, an opening 204 which is formed in the shell 203 to expose upper and lower surfaces of the disc 203 and a shutter 205A which is slidably mounted on the shell 203 to selectively open and close the opening 204. When recording or reading is needed, the shutter 205A is slid to open the opening 204 and a recording/reading head (not shown) is brought into the opening 204 to carry out recording information to the disc 202 or reading information from the disc 202.
The known shutter 205A is made of a metal plate, such as stainless steel plate (SUS) or the like and constructed to have a generally U-shaped cross section. On an upper surface of the shutter 205A, there is formed an indication area 206A where characters and figures (or given patterns), such as the name of maker of the disc cartridge 201, specification of the disc 202 and the like, are printed. Usually, the characters and figures are printed on the indication area 206A using an ultraviolet-sensitive ink and then cured in a certain condition. In this case, printing and curing devices are inevitably needed, which however brings about increase in cost of the disc cartridge 201.
In FIGS. 13 and 14, there is shown another known shutter 205B which is to be slidably mounted on the shell 203 (see FIG. 12) in the same manner as is described hereinabove. As is seen from FIG. 13, on an upper surface of the shutter 205B, there is also formed an indication area 206B. However, the indication area 206B of this shutter 205B is provided by stamping (or pressing) given portions 207 of the upper surface with a lo stamping die having a rough work surface. Due to the stamping, each given portion 207 has a rough surface. The given portions 207 having such rough surfaces are arranged to surround given non-rough portions of the indication area 206B in such a manner that the given non-rough portions constitute given characters or figures which stand out against the background (viz., the given portions 207 having rough surfaces) of the indication area 206B. In case of this shutter 105B, only a stamping machine is needed for providing the shutter 105B with the indication area 206B.
However, even the shutter 105B has the following shortcomings.
(1) Due to the nature of the indication area 206B provided by the stamping, it sometimes to fail to give a satisfied visibility and clarity of the characters and figures to viewers. Particularly, when the metal plate of the shutter 205B has not a sufficient thickness, the visibility and clarity of them become much poor because in such case, the roughness of the stamped given portions 207 becomes too fine to provide clearly defined non-rough portions on the indication area 206B, by which the given characters or figures stand out against the background of the indication area 206B.
(2) Furthermore, as is shown in FIG. 14, when the indication area 206B has a plurality of stamped portions 207 formed thereon, the indication area 206B tends to swell out as is indicated by phantom lines. That is, due to provision of such numerous stamped portions 207, the outside surface area of the indication area 206B is increased causing such undesirable outward expansion.